Raise warnings/infos on tight slice rules

[lmckenzi]

(from https://jira.hl7.org/browse/FHIR-13461)

slicing.rules=openAtEnd and/or slicing.ordered=true should raise an error if declared on any element with max=1 (as there is no notion of 'end' for polymorphic resources).

slicing.rules=openAtEnd and/or slicing.ordered=true should raise a warning on any element with max= 1 if orderMeaning is null because forcing elements to appear in a particular order when order has no meaning breaks interoperability unnecessarily.

slicing.rules=closed should spit out a 'best practice' warning advising that closing slices may increase costs by preventing implementers from constructing instances that satisfy multiple profiles and that ignoring unexpected slices may be preferable to rejecting them.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.